Homicide detectives and crime technicians inspected the crime scene Friday and left. Large streaks and drops of blood remained on walls and the carpet. About 1:45 a.m. Saturday, long after police had gone, neighbors woke up to the home on fire.

Someone passing by called 911 before the fire grew into a serious threat, said Charles Gorham, the carriage house's owner, who lives in a house a few feet from the small backyard apartment.

Fire crews responded and put the fire out not long after it was reported.

"Investigators believe the fire was deliberately set," Baltimore police spokesman Detective Jeremy Silbert said. "This information is very preliminary, but investigators are exploring the possibility that the … fire was set in an attempt to destroy evidence at the initial crime scene."

Homicide detectives and arson investigators are teaming up on the investigation, Silbert said.

Gorham said he believes Mitchell's killer set the fire.

"I think they're trying to cover up their tracks and cover up some evidence," Gorham said. "They had to be young and dumb to think the police hadn't come here already and gotten evidence," he said.

Over the last three years, Gorham had housed Mitchell, who had grown up in the neighborhood, because he said he knew Mitchell was homeless and needed help. Mitchell, 53, had struggled with drug use, according to those who knew him. He had a record of arrests and convictions on multiple drug offenses, according to state court records.

Gorham said he was told workers would come by to board the house up but said Sunday no one showed up.

Gorham said he doesn't feel threatened. He said his work as a minister has taught him not to be afraid of desperate people but to try and help them, instead.

"There's nobody after me," he said. "I don't have any fear if somebody was after me."

Police did not say whether the department was providing Gorham with additional security or whether investigators believe that he needed protection.

While firefighters told Gorham they thought the fire didn't cause extensive damage, he said, he plans to tear the carriage house down.

"I was just telling my wife, I think I'll tear it down and put up a garden back there or grass," he said.

Baltimore police are asking anyone with information on the homicide or suspected arson to call 410-396-2100.